Conventionally, a control system of an electric vehicle that determines abnormalities of sensors by having a composition of a double-sensor system is known (refer to Japanese Patent Application Laid-Open Publication No. H8-205303, for example).
A rotational speed detected by one of the rotational speed sensors is calculated based on information sampling an encoder pulse, and another rotational speed from another one of rotational speed sensors is calculated based on information sampling another encoder pulse.
Then, when a deviation of these two calculated results is smaller than a predetermined value, it is determined that the sensors are normal, and when the results is larger than the predetermined value, it is determined that abnormalities have arisen in the sensors.
In the composition of the Publication No. H8-205303 mentioned above, since two sensors are needed, it is necessary to secure a mounting space for these two sensors, while the mounting space needs to be expanded in order to detect the abnormalities of the sensors, and there is a problem that cost of components and cost of the whole product increase.